The present invention relates to an apparatus for switching off a load change valve of an internal combustion engine comprising a cam shaft with at least one cam disc and a pivot lever supported at the engine which is pivoted by the cam disc. An actuator is moveably guided within the pivot lever for actuating the valve. The coupling member is moveably guided within the pivot lever and has a coupling position and a decoupling position. In the coupling position it rigidly couples the actuator to the pivot lever and in the decoupling position it releases the actuator for movement relative to the pivot lever for switching off the valve. A device for moving the coupling member from the coupling position into the decoupling position and device versa is provided.
In the recent past, reduction of fuel consumption, especially for passenger cars, has been an important consideration for the respective internal engine design. One possibility for achieving this is a partial shutdown of individual cylinders so that the remaining cylinders during partial load operate at increased average pressure and thus have a reduced specific consumption. For shutting down the cylinders it is not only necessary to provide for an interruption of the fuel supply, it is furthermore expedient to interrupt the load flow through the respective cylinder by shutting down the one or more load change valves, especially the intake valve of the respective cylinder.
A device of the afore mentioned kind is known from German Patent application 196 27 390. For movement of the coupling components from the coupling position into the decoupling position a hydraulically operating actuating device is provided which moves upon its actuation the coupling component into the decoupling position by overcoming the force of a pretensioning device. One of multiple problems of this known device is that an exact phase-aligned actuation of the actuator is required because a movement of the coupling component from the coupling position into the decoupling position and vice versa is possible only when the valve is closed, respectively, the base contour of the cam of the cam shaft is effective.
From German Patent application 42 353 21 a valve drive with two alternatively actuatable cams for load change valves of internal combustion engines is known in which a valve has coordinated therewith a first cam for slightly opening the valve and a second cam for a wider degree of opening. A transmission element is coordinated with the first cam and is supported by a play compensation at the valve. A transmission lever supported at the cylinder head engages the second cam and is supported by a switchable follower device indirectly at the valve. The follower device is arranged between the transmission lever and the transmission element. A tappet is slidably and tangentially guided within the transmission lever and is supported at the valve by a play compensation device. The transmission lever can be coupled in a form-locking manner to the tappet by a switchable follower device arranged in the lever. When the tappet is either directly in contact with the first cam the follower device is inactive with a face thereof that is facing away from the valve or indirectly via the transmission lever. The follower device is embodied in the form of balls that can be moved into annular grooves at the tappet by slidable locking elements. The locking elements are hydraulically activated. This known valve drive also has the problem that the hydraulic actuation of the locking elements must be precisely phase-coordinated in order to prevent damage to the engine.
It is therefore an object of the present invention to improve a device of the aforementioned kind such that it is reliably ensured that switching off of the load change valve takes place especially when the base contour of the cam disc for actuation of valve is effective, i.e., when the pivot lever does not exert a force onto the actuator.